When I started experimenting with 40 degree shoulder 6BR back in 2015 it was not to find something more accurate than the Dasher, it was to find something that was EASIER THAN THE DASHER. I had turned, prepped, and blown out hundreds of Dasher brass years ago. It was all at the end of its life now. I had always noticed with a max load in the Dasher it still did not fill the case, there was always more space in the case. PPC shooters wanted a full case! So why were we blowing the case out and strething it so much? I had heard the 40 degree shoulder makes for a “perfect boiler room” to burn the powder more effieciently and completely. I think of it like a car engine’s combusion chamber. Think of a street car vs a NASCAR piston chamber, change the piston’s head angles qnd you get a more effiecient combustion chamber and more HP out of the same displacement. I don’t know all the correct engine terms here, but I hope you get the point. In 2015, I had shot BR long range many years and I did not want to spend so much time making Dasher brass again, so I took a 6BRDX finish reamer I had and ran it in a standard 6BR barrel I had to just enough to make a 40 degree shoulder to experiment with. I quickly found the brass was easy to make and kept the long standard BR neck. Maybe it was a fast barrel, but I chrongraphed Berger 105 Hybrids up to 3050fps with only very mild pressure signs, not enough to ruin the brass after many firings. But I found accuracy was between 2920-2970fps, faster than that and groups definitely started opening up. The barrel as a BR would start showing pressure after 2900fps. I then rechambered another std 6BR barrel the same way to confirm my findings. It had been a good shooting 6BR barrel. This barrel started off shooting better with the 40 degree shoulder than it had with standard BR chambering. I found it easier to tune than any st BR or Dasher I had ever had. The first time out I shot two or three groups in row in the 0.8 inch range at 500 yards WITH different powder charges! I had never had a Dasher or standard BR shoot that good. This was enough info. for me to now to have a reamer made.
I found the 6BRAI (I call it) easier to tune and much easier to make good cases. It kept the long BR neck. Fire forming rounds were very accurate and brass could be fully expanded after one firing. With Dasher brass I like to FF twice at a low powder charge or I would lose primer pockets early. The AI reamer I had made was a .272 no turn and was made to have a “crush fit” of 4 thou. (0.004) for std. 6BR cases just like P.O. Ackley use to recommend. The FF round head spaces on the neck shoulder junction, so no need for false shoulders or necking way down to get a lot of tension so you can set the round in the rifling hard tO FF the Dasher.
With all this said. Do I think the 6BRAI is more accurate than the DASHER? Probably not. Like said before, accuacy has more to do with a great barrel matched with great bullets, ALSO, a great shooter shooting in good conditions. The question to me is: WHICH ONE IS EASIER TO MAKE AND TUNE? To me that easily goes to the 6BRAI. Unless you are very experienced with the Dasher, you will be able to make very good 6BRAI fire formed rounds much faster and easier than you vrs the DASHER, this should lead to better accuracy for the less experienced shooters.
Note: I have just about quit posting on here for people picking my posts apart. I don’t pick other peoples posts apart! I don’t claim to know it all, I am still learning, this is all my opinion based on my findings, please be respectful!
Samuel Hall
Good shooting...James
